Proceedings of the X International Symposium on Biological Control of Weeds

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Leafy spurge (Euphorbia esula L.) is a deep-rooted, perennial weed with erect stems 40 to 80 cm tall. The weed reproduces by both vegetative buds and the production of large quantities of seeds. A native of Eurasia, leafy spurge was first reported in the state of Massachusetts in 1827. Leafy spurge now occurs abundantly on the northern Great Plains of the United States and the prairie provinces of Canada, where it often forms stands dense enough to displace native plants and restrict cattle grazing. Biological control of leafy spurge in the United States began in the 1960s with the introduction of Hyles euphorbia. Fifteen nonindigenous insect species have been approved for release in the United States for the control of leafy spurge. Different biological control agents affect the leafy spurge plant in different ways. Primary methods of attack include consumption of above-ground plant material, consumption of root material, and blocking seed production. Aphthona sp. flea beetles have produced the greatest impact on leafy spurge. A. nigriscutis and A czwalinae/lacertosa impact the plant by ovipositing eggs at the base of the plant. The resulting larvae feed on leafy spurge roots, increasing plant morbidity, reducing plant health and creating pathways for the introduction of plant pathogens. Data collection indicates that flea beetles can reduce leafy spurge stem densities by as much as 80%-90% over large areas. While leafy spurge continues to increase in the United States, techniques for control-while still evolving-continue to improve. Measuring the success of biological control has traditionally been approached from the perspective of agent/host interactions. Too often our perception of success or failure is predetermined by how we choose to view the problem. Multiple dimensions of success exist when one views the issue from a broader perspective. We must evaluate the success of weed control in terms of biological, ecological, scientific, social, economic, political and legal success. Evaluation of leafy spurge control in each of these thrust areas indicates that the program has been successful, at least in part. However, a great deal of work remains in several other problem areas. Successful leafy spurge control is on the horizon. How long it will take to be realized depends on our commitment to solving the problem and our willingness to work as a cohesive team in each of the major thrust areas.